首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   83091篇
  免费   8196篇
  国内免费   160篇
耳鼻咽喉   1185篇
儿科学   2528篇
妇产科学   1789篇
基础医学   11852篇
口腔科学   2010篇
临床医学   10202篇
内科学   14650篇
皮肤病学   1295篇
神经病学   6734篇
特种医学   2889篇
外国民族医学   10篇
外科学   11421篇
综合类   1689篇
一般理论   67篇
预防医学   9487篇
眼科学   1852篇
药学   6761篇
  1篇
中国医学   77篇
肿瘤学   4948篇
  2021年   1114篇
  2020年   738篇
  2019年   1120篇
  2018年   1398篇
  2017年   1007篇
  2016年   1096篇
  2015年   1247篇
  2014年   1646篇
  2013年   2580篇
  2012年   3472篇
  2011年   3744篇
  2010年   1989篇
  2009年   1911篇
  2008年   3232篇
  2007年   3546篇
  2006年   3418篇
  2005年   3478篇
  2004年   3255篇
  2003年   3024篇
  2002年   2960篇
  2001年   2720篇
  2000年   2829篇
  1999年   2516篇
  1998年   1092篇
  1997年   904篇
  1996年   894篇
  1995年   805篇
  1994年   832篇
  1993年   751篇
  1992年   2096篇
  1991年   2023篇
  1990年   1897篇
  1989年   1867篇
  1988年   1780篇
  1987年   1788篇
  1986年   1694篇
  1985年   1675篇
  1984年   1392篇
  1983年   1265篇
  1982年   840篇
  1981年   722篇
  1979年   1214篇
  1978年   873篇
  1977年   762篇
  1976年   719篇
  1975年   715篇
  1974年   859篇
  1973年   752篇
  1972年   733篇
  1971年   640篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
We sought to define objective indicators of the resolution of Pseudomonas aeruginosa endobronchial infection in patients with cystic fibrosis. We prospectively studied 75 patients admitted for treatment of a pulmonary exacerbation and quantitated sputum bacterial density, DNA content, and the concentration of albumin and total protein in sputum, and compared these values with clinical evaluation. Eleven of the 75 patients had systemic signs, fever, and leukocytosis, which we arbitrarily defined as due to endobronchial infection. At the end of hospitalization, these 11 patients were afebrile, had peripheral leukocyte counts in the normal range, and were judged improved. Sputum P. aeruginosa density, DNA content, and total protein content on admission were similar in the two illness groups. Hospitalization and parenteral antibiotic administration for an average of 14.6 days were associated with improved pulmonary function in all 75 subjects (P values for forced vital capacity, forced expiratory volume at 1 second, and peak expiratory flow rate were all less than 0.001). With improvement, there was a decrease in sputum P. aeruginosa density (mean of both groups decreased from 10(7.80) CFU/g on admission to 10(5.96) CFU/g; P less than 0.001), and a decreased DNA concentration (overall mean 4.73 +/- 4.75 on admission to 2.76 +/- 2.49 mg/g; P less than 0.002). The decrease in sputum total protein concentration for both groups was not significant (overall mean 60.5 +/- 48.4 to 43.9 +/- 38.2 mg/g; P = 0.06). Sputum albumin concentrations did not change in either group. We conclude that in cystic fibrosis subjects with a pulmonary exacerbation, bacterial density, sputum DNA and protein content decrease with hospitalization and parenteral antibiotic therapy. At the end of treatment, these indices of sputum infection and inflammation correlate with improved pulmonary function and clinical improvement. These changes are independent of the presence or absence of fever on admission.  相似文献   
992.
Using the Rutter Behavior Questionnaire, schoolteachers assessed the frequency of common abnormal behavior in 544 8-year-old children with phenylketonuria who were born in the United Kingdom and in whom the diagnosis was made by routine testing in infancy, either during the early years of screening (cohort 1, births 1964 to 1971) or after a national reorganization of the program (cohort 2, births 1972 to 1977). All children received treatment before 4 months of age. Two matched control subjects were assessed for each patient. Compared with the controls, patients in cohorts 1 and 2 receiving a strict low-phenylalanine (phe) diet (average phe concentration less than 600 mumol/L) were 1.5 and 1.7 times, respectively, more likely to have deviant behavior; those receiving a less well controlled diet were 2.5 and 1.9 times, respectively, more likely to show such behavior. Patients more often had mannerisms, hyperactivity, and signs of anxiety and were less responsive and more solitary than were controls. On the other hand, they were not more aggressive, untruthful, or disobedient, nor absent from school more frequently. The increased frequency of deviant behavior may be the result of both psychologic stress and neurologic impairment.  相似文献   
993.
994.
To date the response rates to biomodulated 5-fluorouracil in patients with metastatic or unresectable colorectal carcinoma have been varied. Potentially responsive patients are difficult to identify and treatment schedules are both expensive and toxic. Thus, any method that could be used to predict patient response would be both clinically and economically valuable. Increased p53 protein levels have previously been shown to correlate with disease progression in a series of colorectal carcinoma patients treated with 5-FU/folinic acid biomodulated chemotherapy. In addition to mutation of the p53 tumour suppressor gene, mutation of the K-ras gene at codon 12 has also been shown to be a frequent occurrence in the step-wise progression from normal colonic mucosa to adenocarcinoma. Oncogenic activity in the ras family has recently been shown to correlate with decreased levels of apoptosis and thus increased resistance to both radiation and certain chemotherapeutic agents. The aim of the present study was therefore to investigate if a correlation existed between mutation of the K-ras gene at codon 12 and disease progression in the series of colorectal carcinoma patients previously evaluated for levels of p53 protein expression. Response to 5-FU/folinic acid was assessed radiologically by CAT scan (WHO criteria) and clinically by Karnofsky performance scale (KPS) 3 months after the initial treatment. The presence of a K-ras gene mutation was assessed with radiolabelled oligonucleotide probes on amplified patient DNA, dot blotted on to a nylon membrane. Fifty-two patients were assessed and 25% were found to possess mutations at codon 12 of their K-ras gene. In contrast to increased levels of p53 protein, K-ras mutation at codon 12 did not correlate with disease progression when assessed either radiologically or clinically.  相似文献   
995.
996.
OBJECTIVE: To demonstrate that individualized optimal fetal growth norms, accounting for physiologic and pathologic determinants of fetal growth, better identify normal and abnormal outcomes of pregnancy than existing methods. METHODS: In a prospective cohort of 38,033 singleton pregnancies, we identified 9,818 women with a completely normal outcome of pregnancy and characterized the physiologic factors affecting birth weight using multivariable regression. We used those physiologic factors to individually predict optimal growth trajectory and its variation, growth potential, for each fetus in the entire cohort. By comparing actual birth weight with growth potential, population, ultrasound, and customized norms, we calculated for each fetus achieved percentiles, by each norm. We then compared proportions of pregnancies classified as normally grown, between 10th and 90th percentile, or aberrantly grown, outside this interval, by growth potential and traditional norms, in 14,229 complicated pregnancies, 1,518 pregnancies with diabetes or hypertensive disorders, and 1,347 pregnancies with neonatal complications. RESULTS: Nineteen physiologic factors, associated with maternal characteristics and early placental function, were identified. Growth potential norms correctly classified significantly more pregnancies than population, ultrasound, or customized norms in complicated pregnancies (26.4% compared with 18.3%, 18.7%, 22.8%, respectively, all P<.05), pregnancies with diabetes or hypertensive disorders (37.3% compared with 23.0%, 28.0%, 34.0%, respectively, all P<.05) and neonatal complications (33.3% compared with 19.7%, 24.9%, 29.8%, respectively, all P<.05). CONCLUSION: Growth potential norms based on the physiologic determinants of birth weight are a better discriminator of aberrations of fetal growth than traditional norms. LEVEL OF EVIDENCE: II.  相似文献   
997.
OBJECTIVE: To assess the utilization rates of and complications associated with inpatient hysterectomy in California between 1991 and 2004. METHODS: We used the California Patient Discharge Database to analyze International Classification of Diseases, 9th Revision, Clinical Modification diagnostic and procedure codes for 649,758 women undergoing inpatient hysterectomy in California between 1991 and 2004 using multiple logistic regression models. RESULTS: Between 1991 and 2004, the incidence of any type of inpatient hysterectomy for benign gynecologic conditions declined 17.6%. The rates of laparoscopically assisted vaginal hysterectomy and subtotal hysterectomy increased substantially. The year of hysterectomy was a factor associated with both medical and surgical complications; the odds of inpatient complications between 1991 and 2004 steadily declined. CONCLUSION: In California between 1991 and 2004, the incidence of inpatient hysterectomy for benign gynecological conditions and the adjusted odds of complications declined substantially. Changes in practice and shorter hospital stays may have affected the changes in inpatient hysterectomy rates and associated inpatient complications.  相似文献   
998.
999.
IntroductionPeople with sexual interests in bondage and discipline, “sadomasochism” or dominance and submission (BDSM) have been seen by many professionals as damaged or dangerous.AimTo examine sexual behavior correlates of involvement in BDSM and test the hypothesis that BDSM is practiced by people with a history of sexual coercion, sexual difficulties, and/or psychological problems.MethodsIn Australia in 2001–2002, a representative sample of 19,307 respondents aged 16–59 years was interviewed by telephone. Weighted data analysis used univariate logistic regression.Main Outcome MeasuresSelf-reported demographic and psychosocial factors; sexual behavior and identity; sexual difficulties.ResultsIn total, 1.8% of sexually active people (2.2% of men, 1.3% of women) said they had been involved in BDSM in the previous year. This was more common among gay/lesbian and bisexual people. People who had engaged in BDSM were more likely to have experienced oral sex and/or anal sex, to have had more than one partner in the past year, to have had sex with someone other than their regular partner, and to have: taken part in phone sex, visited an Internet sex site, viewed an X-rated (pornographic) film or video, used a sex toy, had group sex, or taken part in manual stimulation of the anus, fisting or rimming. However, they were no more likely to have been coerced into sexual activity, and were not significantly more likely to be unhappy or anxious—indeed, men who had engaged in BDSM scored significantly lower on a scale of psychological distress than other men. Engagement in BDSM was not significantly related to any sexual difficulties.ConclusionOur findings support the idea that BDSM is simply a sexual interest or subculture attractive to a minority, and for most participants not a pathological symptom of past abuse or difficulty with “normal” sex. Richters J, de Visser RO, Rissel CE, Grulich AE, and Smith AMA. Demographic and psychosocial features of participants in bondage and discipline, “sadomasochism” or dominance and submission (BDSM): Data from a national survey.  相似文献   
1000.
Uterine rupture, whether in the setting of a prior uterine incision or in an unscarred uterus, is an obstetric emergency with potentially catastrophic consequences for both mother and child. Numerous studies have been published regarding various risk factors associated with uterine rupture. Despite the mounting data regarding both antepartum and intrapartum factors, it currently is impossible to predict in whom a uterine rupture will occur. This article reviews the data regarding these antepartum and intrapartum predictors for uterine rupture. The author hopes that the information presented in this article will help clinicians assess an individual's risk for uterine rupture.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号